The present invention relates to improvements in actuating mechanisms for plunger type switches, and more specifically improvements which make the mechanism water resistant.
U.S. Pat. No. 5,446,252, issued Aug. 29, 1995, discloses an actuating mechanism for a plunger type switch which is particularly well adapted for use as a limit switch or proximity sensor and which may be positioned in relatively narrow spaces. The length of a plunger-type switch (the dimension of the switch extending along the axis of the plunger) is generally considerably greater than the thickness of the plunger-type switch. Therefore, to ensure minimum thickness of the limit switch, the actuating mechanism should translate a force applied perpendicular to the axis of the plunger to a force directed coaxially with the plunger.
In the actuating mechanism disclosed in U.S. Pat. No. 5,446,252, a bowed length of spring steel is used to translate a force directed perpendicular to the axis of the switch plunger to a force directed coaxially with the plunger. The bowed spring is secured within a housing along with the plunger-type switch such that a first end of the spring is spaced in close proximity to or in engagement with the plunger in the extended position. A middle or bowed portion of the spring extends above an upper surface of the housing through an opening or slot. The second end of the spring abuts against the housing (or a set screw) at an end of the opening or slot opposite the first spring end. Ends of the spring are turned upward to form feet for engaging the plunger or the housing or a set screw extending through the housing.
Application of an external force to the middle or bowed portion of the spring directed towards the upper surface of the housing changes the position of the plunger and more specifically advances the first spring end toward the switch a distance sufficient to move the plunger to the retracted position. Upon removal of the external force, the spring returns to its original bowed state such that the first end of the spring advances away from the switch and the plunger is allowed to move to the extended position.
Although the actuating mechanism works well for its intended purpose of providing a limit switch positionable in relatively narrow spaces, there remain needs for improvements to the actuating mechanism to increase its life. For example, there remains a need for such a switch actuator which resists migration of water or other liquids through the housing and into the plunger type switch and electrical connections, without unnecessarily increasing the thickness of the actuating mechanism.